1. Field of the Invention
The present invention relates to computer monitors, and more particularly to an apparatus for controlling the power management of a display monitor that operates to reduce power consumption of the monitor as well as to indicate its corresponding operating mode.
2. Description of the Related Art
Generally, a monitor for a computer system displays information or images on its screen according to signals supplied by the video output of the computer. The supplied video signals include a color picture signal (R,G,B) and a horizontal synchronization signal (HSYNC) and a vertical synchronization signal (VSYNC). According to the DPMS (Display Power Management Signaling) system established by the Video Electronics Standard Association (VESA), the HSYNC and VSYNC signals are not supplied to the monitor when the computer is in an inactive state for a predetermined time followed by the suspend mode and stand-by mode time intervals. In this case, the monitor enters the power-off mode that will reduce the electrical power consumed by the monitor to below five watts.
An earlier power management control apparatus includes a power supplying section and a microcomputer based controlling section. The power supplying section includes a power supply unit for converting an AC input to a DC output, a voltage regulator for generating a constant output voltage, a transformer for generating necessary operating voltages for each part of the monitor, and first and second auxiliary power supplying units coupled to the secondary of the transformer for generating backup voltages.
Also, the controlling section includes a signal input port connected to the video output of the computer, a microcomputer operated in response to the video input signal to produce a power control signal and a mode indicating signal, a feedback circuit provided between the output of the transformer and the regulator, and a mode indicator for indicating the operating mode of the monitor.
In this arrangement, the regulator regulates the output voltage from the power supply depending on the feedback current fed from the secondary of the transformer through the feedback circuit. When the sync signals are not supplied to the video input port and the monitor is in the power-off mode, the power control signal generated by the microcomputer is supplied to the feedback circuit to control the amount of feedback current supplied to the regulator. Then, the regulator lowers the output voltage supplied to the transformer which also lowers all of the output voltages produced at the secondary of the transformer.
With this, the power supplied to the heater of the cathode ray tube or color display tube is lowered, thus reducing the power consumption in the monitor as required in the power-off mode.
Also, the video signal received at the input port is amplified by a signal amplifier and the processed signal is supplied to the signal input of the color display tube. The mode indicator indicates each operating mode, that is, standby, suspend, ON and OFF modes, via two different colored light emitting diodes in response to the mode indicating signal generated by the microcomputer. Normally, one green light emitting diode light being on corresponds to the normal ON mode, one orange light emitting diode light being on corresponds to the standby mode, and both the green and orange light emitting diodes toggle on and off alternately in the suspend mode, and only the orange light emitting diode toggles on and off in the OFF mode.
The above noted apparatus has shortcomings in that first and second auxiliary power supplying units are needed in order to produce the backup voltages supplied to the regulator and the microcomputer when the output voltages produced by the secondary of the transformer are lowered in the power-off mode.
The provision of the first and second auxiliary power supplying units is difficult since they are operated with the power transformer. Thus, securing reliability of each auxiliary power supplying unit is difficult and providing the auxiliary power supplying units in the power management apparatus results in an increase in the manufacturing cost.
The following patents each disclose features in common with the present invention but nevertheless do not teach or suggest the specifically recited combination of features of the present invention:
U.S. Pat. No. 5,579,252 to Huang, entitled Computer Monitor Power-Saving Device, U.S. Pat. No. 5,576,738 to Anwyl et al., entitled Display Apparatus With Means For Detecting Changes In Input Video, U.S. Pat. No. 5,555,032 to Kung, entitled Integrated Circuit For Economizing Power Consumption Of A Monitor By Using Two Reference Values For Discriminating The Input Signal, U.S. Pat. No. 5,548,764 to Duley et al., entitled Power Interrupt Device With Remote Activity Detector, U.S. Pat. No. 5,481,732 to Shahbazi, entitled CRT Monitor Power Control Unit, U.S. Pat. No. 5,481,299 to Coffey et al., entitled Power Saving Device For Video Screen, U.S. Pat. No. 5,465,366 to Heineman, entitled Power Control Module For Computer Monitors, U.S. Pat. No. 5,389,952 to Kikinis, entitled Low-Power-Consumption Monitor Standby system, U.S. Pat. No. 5,375,245 to Solhj ell et al., entitled Apparatus For Automatically Reducing The Power Consumption Of A CRT Computer Monitor, and U.S. Pat. No. 5,065,357 to Shiraishi et al, entitled Data Processing Machine With Liquid Crystal Display And Control Means For Regulating Backlighting To The Display.